The invention relates to improvements in expandible elastic clamping straps (also called clamps, hose clamps, clips, spring clips or nipple clasps), especially to improvements in straps which can be used with advantage to sealingly secure the end portions of hoses to pipes, nipples or other tubular bodies.
U.S. Pat. No. 4,425,681 to Ilius discloses a strap or clamp wherein one end portion of an annular steel band extends into a circumferentially extending slot of the other end portion and the intermediate portion of the strap has two circumferentially extending slots which taper in opposite directions. The width of the slot in the one end portion of the strap is substantially constant, the same as the width of the other end portion. One slot in the intermediate portion of the strap tapers in a direction away from the first end portion toward the second end portion, and the other slot of the intermediate portion tapers in the opposite direction. The end portions of the patented strap or clamp are provided with outwardly extending lugs which can be engaged by the jaws of pliers to move toward each other and to thus increase the diameter of the strap. This renders it possible to slip the expanded strap onto the end portion of a hose or to readily disengage the strap from the hose. The strap tends to reduce its diameter and to thus bear against the external surface of the end portion of the hose which is thereby biased against the external surface of a pipe, nipple or another tubular body.
A drawback of the patented strap or clamp is that its bias upon the end portion of the hose is not uniform all the way around. Measurements indicate that the bias of the band upon a hose or another deformable object is rather pronounced in the region where the two end portions are interdigitated (i.e., in the region of the slot in the one end portion) but that the bias is much less pronounced in the region substantially diametrically opposite the two end portions, namely between the slots in the intermediate portion. The sealing action of the strap increases at an unpredictable rate from the region of minimum bias toward the end portions of the strap. The area of contact between the hose and the internal surface of the strap in the region of the interdigitated end portions equals or approximates the area of contact between the hose and the strap in the region diametrically opposite the end portions. Thus, and based on the results of measurements, the force exerted by the strap per unit area of the external surface of the hose in the region diametrically opposite the end portions of the strap is a fraction of the force per unit area of the hose in the region of the end portions of the strap. This is undesirable in many instances, e.g., when the strap is used under the hood of a motor vehicle to secure a hose to a nipple or to another tubular body. In other words, the sealing action of the strap should be uniform, or at least substantially uniform, all the way around the end portion of a hose which is engaged and deformed by the strap.